In order to protect hydraulic devices connected at a work port, typically a pressure relief valve is placed in parallel with the workport. The pressure relief valve typically partially or totally exhausts to tank flow going to the workport during pressure limitation. Relief valves are used in some oil and gas applications to prevent leakage of subsurface fluids.
Leakage of subsurface fluids may pose an environmental threat if released from the wellbore. Equipment, such as blow out preventers, may be positioned about the wellbore to form a seal about a tubular therein to prevent leakage of fluid as it is brought to the surface. Blow out preventers may have selectively actuatable rams or ram bonnets, such as pipe rams or shear rams that may be activated to seal and/or sever a tubular in a wellbore.